Inside the Star

Pitch drop experiment tests viscosity — and patience

The world’s longest continuously run science project is about to have a big moment. After 87 years, the ninth droplet of pitch, which has taken some 14 years to develop, is about to fall. Somewhere in the world someone will see it happen via web cam.

By comparison, watching paint dry could be considered a Cirque du Soleil spectacle.

“Oh yes, watching paint dry would be far, far more interesting,” says Andrew White, a quantum physicist at Australia’s University of Queensland and custodian of the world’s longest continually run — and slowest — science project.

White is head of the Brisbane school’s “pitch drop experiment,” set up in 1927 to measure the flowing capacity of the hard, black, tar derivative through a glass funnel.

And how slow does pitch flow?

The continent of Australia is drifting faster, says White, who inherited the project last September when its long-time custodian, John Mainstone, died.

“Australia is moving north at six centimetres a year due to continental drift,” he says.

“The pitch drop is 10 times slower than continental drift in Australia.”

Still, the torpid experiment has many Down Under — and around the world via web cam — on the edge of their seats, as they eagerly wait for the project’s ninth drop of pitch to fall.

The glob, which has been forming and falling since the last one escaped in 2000, could go at any time, White says.

“It’s due to drop soon,” he says. “Or maybe in the next six months — or maybe next year.”

Like the two previous scientists to head the experiment, White has had to learn a stoic patience when it comes to pitch.

Pitch is a hard, tarry substance that is so dark it inspired a colloquialism — pitch black.

Derived from wood resins or coal tars, like the stuff in the Alberta oilsands, it is also solid at room temperature.

Indeed, if you whack a chunk of pitch with a hammer, it will shatter like glass.

But as physicist Thomas Parnell set out to demonstrate when he created the project 87 years ago, even in its solid state pitch can actually flow like a liquid — just one with a very high viscosity.

Viscosity is the measure of a fluid’s resistance to flow, or in scientific terms, of the internal friction given it by its molecular makeup.

In kitchen refrigerator terms, honey and mustard have higher viscosities than orange juice or milk.

Heated pitch, which flows more freely, was once commonly used to coat and seal the hulls of wooden boats.

To create the experiment, Parnell took heated pitch — it’s unclear if it was wood or coal based — and poured it into a glass funnel with a sealed stem and placed it all under a bell jar.

After allowing the tarry goo to settle and harden for three years, Parnell lifted the jar, cut the stem seal and then . . . well, then he waited. And waited. And waited.

With a rounded end tapering upward into a slender tail, pitch drops take the shape of normal water droplets. Only they take much, much longer to form and fall.

“For many years, it dropped every eight or nine years and you could pretty reliably guess when it was going to go,” White says.

The introduction of air conditioning into the school’s mathematics and physics building in the 1980s slowed the process considerably, he says.

And each lost drop of pitch meant the stuff remaining in the funnel had less downward pressure on it, White says.

“A lot of the pitch is now gone, probably more than half the pitch, so there’s less pressure pushing down. So it’s flowing less rapidly due to that as well.”

This ninth drop has taken 14 years to approach its falling point.

When it does go, however, White has ensured that it will be unique in that someone, somewhere, will actually see it fall.

He’s trained three web cameras on it, each with independent power sources, and is beaming the watch out on the Internet 24/7.

White says there are some 18,000 subscribers to “The Ninth Watch” webcast, with an average of 200 people tuned into it at any given time.

The elaborate broadcast measures were introduced to overcome a curse that seemed to have attached itself to the drop watch.

For the 1979 event, Mainstone knew a drop was imminent as the tail leading down from the funnel’s spout had become extremely narrow.

“So he stayed in (at the university) Friday night, all day Saturday, Saturday night, until he finally went home exhausted Sunday morning,” White says.

“And when he came in Monday morning, it had dropped.”

For the next drop in 1988, the experiment was moved to the site of a world exposition being hosted by Brisbane, where it proved a popular display.

“It could be seen by thousands of people walking past every few minutes,” White says.

Yet when Mainstone left his drop vigil for a cup of tea, it fell, apparently unseen by anyone, he says.

Then, for the subsequent 2,000 drop, with a video camera trained on it for the imminent fall, there was a power outage at the university.

“During the 20 minutes that we had a blackout due to a thunderstorm, the drop dropped,” White says.

“That’s why this time we have the three cameras on an uninterruptable power supply. So surely this time surely someone is going to see it.”

Lacking rigid environmental controls and observation protocols — it sat in a cupboard for decades — the pitch drop set up is less a proper laboratory experiment than a science demonstration, White says.

Indeed, that’s likely why Parnell first set it up almost nine decades ago, he says.

“It’s hard to know what exactly he was thinking, but he probably just wanted to set up a cheap demonstration to (show) that the world is not always as it seems up front,” White says.

“And this is a really beautiful demonstration that something that is a solid . . . can nevertheless flow like it’s a liquid,” he says.

Still, the first seven drops allowed researchers to make some rough calculations about the viscosity of pitch. According to The Pitch Drop Experiment website, this particular piece of pitch is 100 billion times more viscous than water.

White says the project has gained a “vast amount of attention” both globally and in Australia, where the national sports betting agency briefly ran a book on when the ninth drop would fall.

“But they closed it, unfortunately, before I could get a bet on,” he says.

The project made its biggest splash internationally in 2005, when it earned Parnell and Mainstone the Ig Nobel Prize in physics.

Parodies of the Nobel Prize, the Ig Nobels are administered by the comedic Annals of Improbable Research magazine and recognize scientific work of dubious or trivial worth.

“But I think the time scale really speaks to people,” says White, who says all the previous drops going back to the first in 1937 remain at the bottom of the bell jar.

“You can see the drops that dropped when you were a child, when your parents were children, when your grandparents were children.”

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